San Bruno Neighborhoods by Their Lots: Lot Sizes, Flood Zones and Fire Zones

The City of San Bruno’s public parcel layer carries the San Mateo County assessor’s property use code, year built and lot area for the city’s parcels. We took the 10,227 parcels the assessor codes as a single-family home (with or without an ADU), placed each in our neighborhood guide outlines, checked its center against FEMA’s flood map and checked each lot against CAL FIRE’s fire hazard severity zone maps. Lot sizes are the assessor’s recorded lot areas. The figures come from county assessor records in the City of San Bruno parcel layer, October 2026. There are no addresses or owner details here.

The short answer

• Citywide, the median lot under a single-family house is 5,180 sq ft.
• Largest lots: Rollingwood & Monte Verde (5,840 sq ft), Pacific Heights & Portola Highlands (5,630 sq ft) and Crestmoor & Shelter Creek (5,550 sq ft).
• Smallest: Downtown San Bruno & Belle Air (5,000 sq ft), Huntington Park & Lomita Park (5,000 sq ft) and Mills Park (5,070 sq ft).
• Flood zones: 274 of the 10,227 houses (3%) have their parcel center in a FEMA high-risk flood zone (268 in AE, 3 in AH and 3 in A); the most are in Downtown San Bruno & Belle Air (268) and Huntington Park & Lomita Park (3).
• Fire zones: 3,516 houses (34%) have part of the lot in a CAL FIRE fire hazard severity zone: 1,349 Very High, 1,111 High and 1,056 Moderate. The most are in Crestmoor & Shelter Creek (1,524) and Pacific Heights & Portola Highlands (943).

Neighborhood by neighborhood

Largest median lot first. “Single-family houses” counts parcels the assessor codes as a single-family home whose center falls inside each guide’s outline; no house falls in two guides. Median year built counts the houses with a year on record. Each name opens its guide. Bayhill & Cherry Avenue has no parcels coded as single-family homes, so it’s left out.

The “All of San Bruno” row also counts the 1,138 houses outside the neighborhoods in the table.

What stands out

• Median lots run from 5,000 sq ft to 5,840 sq ft: smallest in Downtown San Bruno & Belle Air and Huntington Park & Lomita Park, largest in Rollingwood & Monte Verde.
• The most fire-zone houses are in Crestmoor & Shelter Creek: 1,524 of its 1,549 houses (98%) have part of the lot in one, 869 of them Very High.
• Most flood-zone houses are in Downtown San Bruno & Belle Air: 268 of its 1,178 houses (23%), in zone AE.
• Year built: the median house was built in 1956 citywide, from 1940 in Downtown San Bruno & Belle Air to 1963 in Pacific Heights & Portola Highlands.

Flood zones, neighborhood by neighborhood

Single-family houses in FEMA high-risk zones inside each guide’s outline, the share of the guide’s houses they make up, and the zones; most first. The other four guides have none.

What the flood zones mean

• Zone A: a 1%-a-year chance of flooding, where FEMA hasn’t set a base flood elevation.
• Zone AE: the same 1%-a-year risk, with a base flood elevation set.
• Zone AH: shallow ponding, usually 1 to 3 feet deep, with the same 1%-a-year risk and a base flood elevation.
• Zone X: moderate to minimal risk, outside the 1%-a-year floodplain.
• Insurance: if the house itself is in an A or V zone, lenders on federally backed mortgages require flood insurance; a flood zone determination for the address settles it. In zone X it’s optional.

Fire hazard zones, neighborhood by neighborhood

CAL FIRE maps how severe the wildfire hazard is across California, in three classes: Moderate, High and Very High. Single-family houses inside each guide’s outline, by the highest zone that touches any part of the lot; most severe first. The other guide has none in any zone.

What the fire zones mean

• Hazard, not risk. CAL FIRE’s Office of the State Fire Marshal says the maps describe hazard: the physical conditions, like vegetation, terrain, fire history, embers and typical fire weather, over 30 to 50 years. They don’t count home hardening, defensible space or fuel reduction, which change the risk to a particular home (OSFM).
• Two kinds of map. Inside city limits (Local Responsibility Areas) we used CAL FIRE’s 2025 map; where the state is responsible for wildfire protection (State Responsibility Areas), its State Responsibility Area map. Land outside the three classes is shown as non-wildland or unzoned (OSFM).
• What a zone can bring. Depending on the zone and the kind of area, stricter building standards for new construction and additions, defensible-space rules, and a line on the seller’s natural hazard disclosure. The city’s building department can say which apply.

Reading it right

• A use code isn’t a zoning district. We counted parcels the county assessor codes as single-family homes, with or without an ADU; townhomes and condos aren’t counted.
• Lot sizes are the assessor’s recorded lot areas, so they can differ from a survey. Year built is the assessor’s too, and 9,333 of the 10,227 houses have one on record.
• We checked the center of each parcel against FEMA’s National Flood Hazard Layer. A lot can straddle two zones, and maps change, so check the current FEMA map for the exact address.
• The flood zone covers the land, not the house. A house can sit above the base flood elevation even in a high-risk zone. An elevation certificate settles it and can lower the insurance price.
• The fire zone describes the land around a house, not how the house is built or how the lot is kept. CAL FIRE’s zone viewer shows any parcel, and a seller’s natural hazard disclosure report states the zones for that property.
• A median isn’t a verdict. It describes the lots, not which neighborhood is right for you.

Go deeper

San Bruno Housing Market by the Numbers covers prices and bidding, San Bruno Neighborhoods Ranked by Price per Square Foot compares the neighborhoods on price, and The Most Expensive Streets in San Bruno & Millbrae goes street by street. Flood & Fire Zones by Neighborhood compares every guide we write, and the San Bruno city guide links every neighborhood guide.

The San Bruno data series: housing market by the numbers · neighborhoods ranked by price per sq ft · where homes sell over asking · ten years of prices by neighborhood · condos and townhomes · house prices by bedrooms · houses under $1.5M · houses at $1.8M and up · the best month to sell · the most expensive streets (with Millbrae)

Buying, selling or rebuilding in a flood or fire zone?

A Property Nerd can pull the zoning, the lot, the flood and fire zones, any elevation certificate and the recent sales on your street before you write an offer, set a price or plan a rebuild. Call (408) 373-1660 or (650) 383-8606, or book a strategy call. Commissions are negotiable, and we offer bundled services, so ask us what’s included.